Engine systems may utilize one or more gas constituent sensors, such as oxygen sensors, for sensing an oxygen concentration of air flowing through engine air passages. In one example, an engine system may include one or more intake oxygen sensors (IAO2) located in the engine intake. For example, an intake oxygen sensor may be positioned in an intake passage, downstream from a compressor and a charge air cooler, to provide an indication of EGR flow. In another example, the engine system may include one or more exhaust gas sensors in an exhaust system of the engine system to detect an air-fuel ratio of exhaust gas exhausted from the engine. Under certain engine operating conditions, such as a cold start or condensate formation, water may splash against and contact the oxygen sensor. When water contacts the oxygen sensor the temperature of the sensor decreases. As a result, heater power of a heating element of the oxygen sensor increases to increase the sensor temperature. When the heater power increases for an extended period of time when water is on the oxygen sensor, the heating element may crack, thereby degrading the oxygen sensor.
In one example, the issues described above may be addressed by a method for adjusting heater power of a heating element of an oxygen sensor in response to an increase in the heater power by a threshold amount. Water droplets may be indicated at the oxygen sensor when the heater power increases above a baseline power level by the threshold level. In this way, heater power may be adjusted to reduce degradation of the heating element of the oxygen sensor due to water at the sensor.
As one example, heater power of the heating element of the oxygen sensor may be decreased responsive to water contacting the heating element. In one example, water contacting the heating element may be indicated when the heater power increases above a baseline power level by a threshold amount. In another example, water contacting the heating element may be indicated when a pumping current of the oxygen sensor decreases by a threshold pumping current amount. In some examples, decreasing the heater power may include turning off the power of the heating element. After a duration of decreasing the heater power, the heater power may be turned back on and increased to the baseline power level. The duration may either be pre-determined or based on when a temperature of the heating element decreases below a threshold temperature, the threshold temperature being a threshold cracking temperature. In this way, reducing the heater power when water is indicated at the oxygen sensor may reduce oxygen sensor degradation via cracking of the heating element.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.